1. Field of the Invention
The present invention relates to an organic electroluminescent display device, and more particularly, to an organic electroluminescent display device and a method of fabricating the same that is capable of preventing moisture from penetrating into the organic electroluminescent display device.
2. Discussion of the Related Art
In general, the organic electroluminescent display (OELD) device emits light by injecting electrons from a cathode and holes from an anode into an emission layer, combining the electrons with the holes, generating an exciton, and transforming the exciton from an excited state to a ground state. Unlike the liquid crystal display (LCD) device, the OELD device does not require an additional light source, and therefore has the advantage of compact volume and light weight.
FIG. 1 is a circuit diagram schematically illustrating an OELD device according to the related art. As shown in FIG. 1, the OELD device includes a gate line “GL” and a data line “DL”, which cross each other to define a pixel region “P”. Also, the OELD device includes a power line “PL” that is parallel to the data line “DL”. On the pixel region “P”, a switching thin film transistor (TFT) “STr”, a driving TFT “DTr”, a storage capacitor “StgC”, and an organic electroluminescent diode “E” are formed. The switching TFT “STr” is formed at a crossing portion of the gate and data lines “GL” and “DL”. The driving TFT “DTr” is electrically connected to the switching TFT “STr” and the organic electroluminescent diode “E”. The organic electroluminescent diode “E” has a first electrode connected to the driving TFT “DTr” and has a second electrode connected to the power line “PL”. The power line “PL” supplies a power voltage into the organic electroluminescent diode “E”. The storage capacitor “StgC” is formed between the gate and source electrodes of the driving TFT “DTr”.
When a voltage is supplied to the switching TFT “STr” through the gate line “GL”, the switching TFT “STr” is turned ON. When another voltage is supplied to the driving TFT “DTr” through the data line “DL” and the switching TFT “STr”, the driving TFT “DTr” is turned ON such that the organic electroluminescent diode “E” emits light. When the driving TFT “DTr” is turned OFF, the storage capacitor “StgC” keeps a voltage for the driving TFT “DTr”. Thus, even if the switching TFT “STr” is turned OFF, a voltage to be supplied to the organic electroluminescent diode “E” is kept by the storage capacitor “StgC”.
FIG. 2 is a schematic perspective view of an OELD device according to the related art. As shown in FIG. 2, the related art OELD device includes first and second substrates 3 and 31 that face and are spaced apart from each other. A seal pattern 40 is formed at edges of the first and second substrates 3 and 31 between the first and second substrates 3 and 31, thereby sealing the OELD device. The first substrate 3 is formed with the driving TFT “DTr”, the switching TFT “STr” (of FIG. 1), and the storage capacitor “StgC” (of FIG. 1). Also, on the first substrate 3, a first electrode 12, a second electrode 16 and an organic luminescent layer 14 are arranged to constitute the organic electroluminescent diode “E” (of FIG. 1). The first electrode 12 is electrically connected to the driving TFT “DTr”. The organic luminescent layer 14 is formed on the first electrode 12 and includes luminescent material patterns 14a, 14b, and 14c. The luminescent material patterns 14a, 14b, and 14c correspond to the pixel regions “P” (of FIG. 1) and have red, green, and blue colors “R”, “G”, and “B”, respectively. The second electrode 16 is formed on the organic luminescent layer 14. The first and second electrodes 12 and 16 serve to create an electric field, by which the organic luminescent layer 14 emits light.
As shown in FIG. 2, the second substrate 31 is spaced apart from the second electrode 16 and includes a moisture absorbent 32 of barium oxide or calcium oxide. Since the organic luminescent layer 14 on the first substrate 3 deteriorates when it is exposed by oxygen or/and moisture, it is necessary to completely seal the first and second substrates 3 and 31 and form the moisture absorbent 23. In the related art, the first and second substrate 3 and 31 are attached using the seal pattern 40 under a condition of vacuum or an inert gas.
However, the related art has some problems. The first and second substrates 3 and 31 may be separated from each other if oxygen penetrates into the device. Also, moisture may penetrate through an interface between the seal pattern 40 and the first substrate 3 or between the seal pattern 40 and the second substrate 31. Moreover, the seal pattern 40 may not have a uniform width. In the event that the seal pattern 40 has a too thin portion, moisture penetrates into the device through that thin portion. In the event that the seal pattern 40 has a too thick portion, the seal pattern 40 may cover the gate line and the data line such that contact looseness occurs.